The present invention relates, in general, to semiconductor packaging, and more particularly, to semiconductor die attachment.
In the past, the semiconductor industry utilized a variety of techniques to attach semiconductor die to semiconductor package leadframes. Typically, equipment commonly referred to as a die bonder is utilized to pick up semiconductor die and attach them to a leadframe using adhesives such as solder or conductive epoxies. Such die bonding equipment is well known in the art and is available from a variety of equipment vendors. One problem with prior die bonding equipment and methods is the inability to accurately control the thickness of the adhesive between a semiconductor die and a semiconductor package leadframe.
Typically, the die bonding equipment has a die bonding head that picks up a semiconductor die, positions it over a semiconductor leadframe, and lowers the semiconductor die down onto the leadframe for attachment. The die attach head typically is attached to the frame by a long arm. The downward movement of the die bonding arm to lower the head is controlled by an adjusting cam or mechanical stop located remotely from the head at the end of the arm and attached to a frame or support of the die attach equipment. Consequently, the control capability of the adjusting cam varies because of the long distance between the adjusting cam and the die bonding head. Consequently, the thickness of the die attach adhesive, commonly referred to as the bond line thickness (BLT), typically has an accuracy of approximately plus or minus fifty microns. This variation in bond line thickness results in variations in the parameters of the semiconductor die attached to the leadframe often causing these parameters to not match the specifications for the semiconductor device. This nonconformity to the specifications results in lower yields and increased manufacturing costs.
Accordingly, it is desirable to have a die attach method that accurately controls the bond line thickness to an accuracy less than fifty microns.